T-Mobile is offering some impressive sales for one day only, and that day is Saturday, February 11. On that date, T-Mobile is offering some of its fastest and newest 4G smartphones for free with a qualifying plan purchase.

If you are wondering what the catch is, you must pay for the device upfront and send off one of those hated mail-in rebates. The offer is good for new and existing eligible customers and includes the Samsung Galaxy S II, the SpringBoard tablet, BlackBerry Bold 9900, and HTC Amaze 4G.

“T-Mobile has a commitment to make the 4G experience affordable and accessible to everyone, so this sweet deal on smartphones and tablets is our Valentine’s gift to consumers,” said John Clelland, senior vice president of marketing, T-Mobile USA. “No matter where loved ones live, T-Mobile wants to bring them closer with unlimited talking, photo sharing, video chatting, texting, and more.”

There are also some specials for people that want to sign up for the Unlimited Value Plan rather than the Classic Plan. T-Mobile offers the Galaxy S II at no charge after mail-in rebate with any down payment of $199.99. The Nokia Lumia 710 is available for a $49.99 down payment and is free after rebate. The Sonic 4G Mobile Hotspot is available for a $24.99 down payment and is free after mail in rebate as well.